Mem 310 Project

The Green Classroom By Jonathan Lando Nevin John Christine Filippone John P.

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Abstract We propose to design an energy saving “green” classroom, utilizing energy saving technologies in the areas of HVAC, lighting, and insulation. We intend to do a cost benefit analysis in each area. The design will be based on assumptions of the weather conditions during winter and summer, and heat loss through doors, windows, and walls. Introduction A green building aims primarily at reducing the energy costs of the building operation. However many other benefits come from building “Green”, such as; “enhancing and protecting ecosystems and biodiversity, improving air and water quality , conserve natural resources, improve student productivity and satisfaction , improve air, thermal, lighting, and acoustic ambiance, and enhance occupant comfort and health.”1 We as a group feel that with the exception of some new construction on Drexel’s campus (Bossone, Drexel Law), the buildings and classrooms on campus do not adhere to the “Green Building” principles outlined by LEED. Planning Each group member was assigned a portion of this report as follows: Jon L.: Title Page Abstract – List the objectives of the project and summarize its accomplishments. Introduction – Discuss the problem statement and the path the team has taken to solve the problem. Design Description (HVAC System) – Describe the thermodynamic specifications and targets; critically evaluate existing products and identify the gaps the project is intended to fill; show how the concepts were evaluated; demonstrate the analysis used for product evaluation and show its details. Nevin:

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Design Description (Lighting) – Describe the thermodynamic specifications and targets; critically evaluate existing products and identify the gaps the project is intended to fill; show how the concepts were evaluated; demonstrate the analysis used for product evaluation and show its details. Impact Statement – State the potential impact of the design project on society and the environment, and comment on any safety related issues.

Christine: Design Description (Insulation) – Describe the thermodynamic specifications and targets; critically evaluate existing products and identify the gaps the project is intended to fill; show how the concepts were evaluated; demonstrate the analysis used for product evaluation and show its details. Impact Statement – State the potential impact of the design project on society and the environment, and comment on any safety related issues.

John P.: Planning – List each team member’s contribution to the project. Conclusions – State the accomplishments of the project, and demonstrate that the project satisfies engineering specifications. Future Work – Suggest further study based on project work.

Design Description Assumptions: Dimensions of classroom: Length = 60 ft

*(this wall is a boundary to the outside environment)

Width = 30 ft Height = 12 ft Classroom location: The classroom is located on the second floor of a building that contains at least three stories. This room shares one wall with the outside environment. It’s remaining three

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walls, floor, and ceiling are shared by additional classrooms adjacent to, below, or above this classroom. Therefore, it will be assumed that this classroom is at thermal equilibrium with its surrounding classrooms and that heat may only be transferred into or out of the room through its single boundary to the outside environment.

Additional classroom features: 6 windows along the outside wall- each has dimensions of 4’x 6’ 40 light fixtures located on ceiling

Temperatures: Ideal classroom temperature to be achieved = 70 ºF Philadelphia, PA climate characteristics: Average high temperatures: Summer (May- October) = 77.43 ºF Winter (Nov- Apr) = 48.9 ºF Average low temperatures Summer (May-October) = 61.10F Winter (November-April) = 33.730F http://www.rssweather.com/climate/Pennsylvania/Philadelphia/2

An important factor in achieving and maintaining desirable thermal conditions in a classroom is the use of appropriate insulation and windows for the room. In the summer or in warm climates, heat will tend to flow or be transferred into cooler areas, or into the classroom. In the winter or in colder climates, the heat will tend to move out of the classroom and into the area of colder air. This behavior is due to conduction, the transfer of energy from the more energetic particles of a substance to the adjacent less energetic ones as a result of interactions between the particles. In the case of air, more collisions of the molecules during random motion are occurring in the warmer air, causing there to be a greater level of energy. This energy is naturally transferred to the areas of lower energy levels (cooler air) through conduction.

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Heat can also be transferred into or out of a classroom by convection. Because air inside the classroom has velocity due to the HVAC system and air outside the classroom may be in motion as well, convection will occur. Convection combines the effects of conduction and fluid motion. It can be described as energy transfer between a solid surface and the adjacent air that is in motion. The rate of heat transfer due to convection is greater when there is greater surface area or there is a greater difference between the temperatures of the surface and the air in motion. The final mechanism of heat transfer to examine is radiation. This is the transfer of heat by the emission electromagnetic waves which carry energy away from the emitting object.3 Thermal radiation is emitted by bodies because of their temperature.4 This is the type of radiation that the sun emits and that can affect the thermal conditions of a classroom. For this project, we will assume that the classroom is very well sealed and that air in motion inside the room remains inside and the air on the outside remains outside. This means that heat loss or transfer due to convection may be neglected. Radiation loss can be minimized by using foilbacked insulation as a radiation barrier.5 Therefore, we will neglect the heat transferred by radiation through the insulated portions of the classroom walls. The heat transferred through the portion of the walls that are windows will be calculated as heat transferred by radiation. In order to combat the natural movement from higher to lower energy levels that occurs during conduction, insulation can be used as a barrier between the two areas air of differing temperatures. The rate of heat transfer by conduction can be calculated by use of the following equation, •

Q cond = k t A in which

∆T , ∆x

A is the area through which the heat transfer occurs, ∆T is the temperature difference

across the wall, ∆x is the thickness of the layer of wall, and

kt is the thermal conductivity of the

material. (thermo book, p 92) Another form of this equation often used in the construction industry is as follows: •

Q=A

∆T R − factor 5

In this equation,

R − factor describes the thermal resistance of the wall.5 This value takes into

account the material, thickness, and density of the insulation. The higher the R-value, the more effective the insulation will be at preventing heat transfer through the wall.6 The illustration below shows how energy moves from an area of higher temperature to an area of lower temperature over time through conduction.

There are several types of materials which can be considered for use as insulation for a classroom. The main types of insulation are blankets made from mineral fibers, blown-in loose fill, sprayed foam, rigid foam, and reflective systems.7 Each type of insulation material has different Rvalues and costs that must be taken into account. A high performance standard fiberglass blanket insulation of 3 ½ inch thickness has an Rvalue of 15 and costs approximately 37 cents/square foot. This type of insulation is usually placed between studs or joists and is easily installed. Loose fill insulation can be made from cellulose, fiberglass, or rock wool.8 Although cellulose, made from recycled paper, has the highest of the loose fill R-values, 20% will settle after installation and must be replaced or the R-value will decrease. Because this insulation will be for a school classroom and low-maintenance is an important factor, rock wool will be considered instead. It has an R-value of about 3.2/inch thickness. (http://www.eere.energy.gov/consumer/your_home/insulation_airsealing/index.cfm/mytopic=11650)

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Sprayed foam insulation can be sprayed, injected, or poured into a wall, often made of concrete block. Because this type of foam insulation fills in all gaps in the wall, it has an increased R-value. A commonly used material in both sprayed foam and rigid foam insulation is polyurethane. This material has an R-value of about 7 ft2 ºF hr/BTU. Reflective insulation is usually made from aluminum foil backed with paper, film, or a layer of air bubbles. (http://www.ornl.gov/sci/roofs+walls/insulation/ins_08.html) This type of insulation is sensitive to the direction of the heat flow and works best to reduce downward heat flow. It may not be as effective in a climate where heat will flow in opposite directions at different times. Also, this type of insulation is mainly useful in hotter climates. Because Philadelphia experiences hot summers in which heat will flow into the classroom and cold winters in which heat will flow out of the classroom, this may not be the best type of insulation for the wall of this room. The R-value for this material is approximately 9.8 for a 5/16 inch layer. The calculations for the heat transferred by conduction as well as costs for each of the materials discussed above are as follows:

High performance standard fiberglass blanket insulation: •

Q summer = •

Q w int er

(576 ft 2 )(70 − 77.43° F ) = 285 BTU / hr = 0.0835kW into room 15 ft 2 ° Fhr / BTU

(576 ft 2 )(70 − 48.9° F ) = = 810 BTU / hr = 0.237kW out of room 15 ft 2 ° Fhr / BTU

Cost of materials

= (576 ft 2 )($0.37 / ft 2 ) = $213.12

Money lost due to unwanted heat transfer: Summer: ($0.0955 / kWh)(4380h)(0.0835kW ) Winter: ($0.0955 / kWh)(4380h)(0.237 kW )

= $34.93

= $99.13

total yearly cost = $134.06 Loose fill insulation (rock wool): •

Q summer =

(576 ft 2 )(70 − 77.43° F ) = 382 BTU / hr = 0.112kW into room 11.2 ft 2 ° Fhr / BTU 7

•

Q w int er =

(576 ft 2 )(70 − 48.9° F ) = 1085 BTU / hr = 0.318kW out of room 11.2 ft 2 ° Fhr / BTU

Cost of materials

= (576 ft 2 )($0.21 / ft 2 ) = $120.96

Money lost due to unwanted heat transfer: summer: ($0.0955 / kWh)(4380h)(0.112kW ) winter: ($0.0955 / kWh)(4380h)(0.318kW )

= $46.85

= $133.02

total yearly cost = $179.87 Sprayed / Rigid foam insulation: •

(576 ft 2 )(70 − 77.43° F ) = 175 BTU / hr = 0.051kW into room 24.5 ft 2 ° Fhr / BTU

•

(576 ft 2 )(70 − 48.9° F ) = 496 BTU / hr = 0.145kW out of room 24.5 ft 2 ° Fhr / BTU

Q summer =

Q w int er =

Cost of materials

= (576 ft 2 )($1.48 / ft 2 ) = $852.48

Money lost due to unwanted heat transfer: summer: ($0.0955 / kWh)(4380h)(0.051kW ) winter: ($0.0955 / kWh)(4380h)(0.145kW )

= $21.33

= $60.65

total yearly cost = $81.98 Reflective insulation: •

(576 ft 2 )(70 − 77.43° F ) = 361BTU / hr = 0.106kW into room 9.8 ft 2 ° Fhr / BTU

•

(576 ft 2 )(70 − 48.9° F ) = 1025 BTU / hr = 0.300kW out of room 9.8 ft 2 ° Fhr / BTU

Q summer =

Q w int er =

Cost of materials

= (576 ft 2 )($0.40 / ft 2 ) = $230.40

Money lost due to unwanted heat transfer: summer: ($0.0955 / kWh)(4380h)(0.106kW ) winter: ($0.0955 / kWh)(4380h)(0.300kW )

= $44.34

= $125.49

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total yearly cost = $169.83

By comparison of these results, it can be determined that using foam insulation will ensure that the least amount of heat will be transferred to or from the room. This means that this classroom would maintain the highest level of thermal efficiency if it is insulated with a foam material. High performance standard fiberglass blanket insulation had the next best values for the rate of heat transfer. Additionally, there is a much smaller material cost for the fiberglass than for the foam insulation and the money lost each year due to undesired heat transfer is not substantially higher for the fiberglass than it is for the foam. Consequently, high performance standard fiberglass blanket insulation will be used in the design and construction of this classroom because it is the most economically feasible option as well as a suitable material to help minimize the flow of heat between the classroom and its outside surroundings.

As important as it is to choose the appropriate wall insulation to help minimize the effects of conduction on the temperature of the classroom, it is equally important to choose the appropriate type of windows for the classroom. The main way in which heat is transferred through a window surface is by radiation. Solar radiation is processed in three ways as it passes through a window. As displayed below, the radiation energy can be reflected, absorbed, or transmitted. 9

The net rate of heat transfer by radiation is described by the following equation, •

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Q rad = εσA(T s − T surr ) , 9

where Ts and Tsurr are the temperature of the glass surface and the surrounding outside air respectively,

A is the are of the surface, σ is the Stefan-Boltzmann constant, and ε is the

emissivity of the surface.(thermo book, p 95) A standard glass window has an emissivity of about 0.85. This means that approximately 85% of the heat absorbed by the window pane will be transferred to the area with a cooler temperature. According to the calculations below, if a standard glass window is used, heat will be transferred into the classroom in the summer at a rate of about 277 W and out of the classroom in the winter at a rate of about 725 W.

An alternative option is to install double-glazed windows with low-e coatings in the classroom. A low-e (low emissivity) window has a thin layer of transparent metal or metal oxide either baked into or sprayed onto the glass to reduce heat transfer. 10 http://www.leeric.lsu.edu/energy/windows/ This still allows all of the sunlight to pass through the window. These low-e windows have emissivity values of around 0.10. As shown in the calculations below, the amount of heat transferred into the classroom in the summer is significantly less with use of the low-e windows than with the standard windows. Similarly, the rate of heat transferred out of the classroom in the winter is significantly less with use of the low-e windows.

Standard windows: • 1m 2 Q rad summer = (0.85)(5.67 x10 −8 W / m 2 K 4 )(144 ft 2 )( )(294.26 4 K 4 − 298.39 4 K 4 ) = −277.16W 2 10.764 ft

• 1m 2 Q rad w int er = (0.85)(5.67 x10 −8 W / m 2 K 4 )(144 ft 2 )( )(294.26 4 K 4 − 282.54 4 K 4 ) = 725.34W 2 10.764 ft

Low-e windows:

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• 1m 2 Q rad summer = (0.10)(5.67 x10 −8 W / m 2 K 4 )(144 ft 2 )( )(294.26 4 K 4 − 298.39 4 K 4 ) = −32.61W 2 10.764 ft

• 1m 2 Q rad w int er = (0.10)(5.67 x10 −8 W / m 2 K 4 )(144 ft 2 )( )(294.26 4 K 4 − 282.54 4 K 4 ) = 85.33W 2 10.764 ft

Although low-e windows generally cost 10 to 20% more than standard glass windows, 30 to 50% can be saved in energy costs associated with heat transfer through the windows over time. (http://www.energycodes.gov/implement/pdfs/lib_ks_energy-efficient_windows.pdf) Use of low-e windows would minimize unwanted heat transfer between the classroom and the environment outside, while only slightly increasing the initial construction cost of materials. Therefore, low-e windows will be used in this classroom for optimal thermal conditions. HVAC A major part of a modern commercial building is the HVAC (heating, ventilation, and air conditioning system). As mentioned before, Philadelphia experiences a large temperature differential from winter to summer, thus an effective heat and air conditioning machine is a necessity. The Vapor-Compression Refrigeration Cycle is the ideal cycle for heating and airconditioning systems. It consists of 4 processes; Isentropic compression in a compressor, constant pressure heat rejection in a condenser, throttling in an expansion device, and constant pressure heat absorption in an evaporator.

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The heat removed from the refrigerated space (QL) is equal to the difference in enthalpies at stages 1 and 4. QL=h1-h4 The heat added to the warm space (QH) is equal to the difference between the enthalpies at stages 2 and 3. QH=h2-h3 The coefficient of performance (COP) for the refrigeration or heat pump cycle is equal to the amount of heat (QL or QH) divided by the net work into the system. COPR = QL/Wnet,in COPHP = QH/Wnet,in There are three types of Heat Pumps; air source, water source, and ground source. Air source heat pumps are impractical in a climate such as Philadelphia’s because their efficiency drops considerably with temperatures below freezing. Ground source heat pumps exchange heat with the earth, and thus their efficiency is not affected by freezing temperatures since the earth maintains a relatively stable temperature above freezing. For this reason, we have decided to implement a ground source heat pump. They tend to be more expensive than air source pumps however, this money is often recuperated in a short amount of time with energy savings. The model we have based our calculations on is the “Carrier 50YD GT-PX Groundwater Heat Pump.” 12 If the desired temperature inside a room is to be 700F, or 21.110C, or 294.11K, assuming the room has the dimensions of (30x60x12) ft, or (9.14x18.28x3.66) m, then the following are the calculations for the COP of the system under the assumed winter and summer conditions in Philadelphia; Winter (November –April) Avg. High Temperature = 48.9 ºF Surface area of fiberglass insulated wall: 576 ft2 Surface area of Low-e windows: 144 ft2 Total room heat loss rate (wall + windows) = 85.567 kW out of the room COPHP = 4.4

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W’net,in = Q’H / COPHP = 85.567 kW / 4.4 = 19.447 kW = total power required by the heat pump to maintain the room at 700F. Assuming that the heat pump will only be operating between the hours of 7am to 9pm (typical class hours) Monday through Friday, a total of 14 hours a day, and considering the average cost of electricity in Pennsylvania is 9.55 cents/kWh, we can easily calculate the operational cost of running the heat pump. (19.447kW)(14 hours) = 272.26 kWh (272.26kWh)($0.0955/kWh) = $26/day It costs $26 a day to heat the room and maintain its temperature at 700F if the outside temperature is 48.90F. For the entire winter, excluding weekends when there are no classes, the operational cost of the heat pump

= ($26/day)(130 days/winter) = $3,380 per winter season. Summer (May – October) Avg. High Temperature = 77.43 ºF Surface area of fiberglass insulated wall: 576 ft2 Surface area of Low-e windows: 144 ft2 Total Heat Gain by Room (wall + windows): = 32.694 kW into room EER = 22 COPR = 6.4478 W’net,in = Q’R / COPR = 32.694 kW / 6.4478 = 5.07 kW = total power required by the heat pump acting in cooling mode to maintain the room at 700F.

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Again assuming that the system will only be operating between the hours of 7am to 9pm (and considering the average cost of electricity in Pennsylvania is 9.55 cents/kWh, the total cost of cooling the room and keeping it at 700F is… (5.07 kW)(14 hours) = 70.98 kWh (70.98 kWh)($0.0955/kWh) = $6.78/day It costs $6.78 a day to cool the room and maintain its temperature at 700F if the outside temperature is 77.430F. For the entire summer, excluding weekends when there are no classes, the operational cost of the heat pump cooling cycle is = ($6.78/day)(130 days/summer) = $881.22 per summer season. When comparing the Ground-Source Heat pump we have selected to a heat pump with a lesser COP (the average pump has a COP of about 2.5-3.5 in heating mode, and an EER of 8-12 in cooling mode), we can figure out how much money Drexel could save by using high efficiency machinery for its heating and cooling needs.

Winter Avg. High Temperature = 48.9 ºF Surface area of fiberglass insulated wall: 576 ft2 Surface area of Low-e windows: 144 ft2 Total room heat loss rate (wall + windows) = 85.567 kW out of the room COPHP= 3.0 W’net,in = Q’H / COPHP = 85.567 kW / 3.0 = 28.522 kW (28.522 kW)(14 hours) = 399.31 kWh (399.31 kWh)($0.0955/kWh) = $38.13/day = ($38.13/day)(130 days/winter) = $4,956.90 per winter season.

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When compared to the carrier heat pump, an increase in COPHP by 1.4, leads to an increase in savings per day of (38.13 – 26) = $12.134/day, and per winter season, a savings of $1,576.9/winter

Summer Avg. High Temperature = 77.43 ºF Surface area of fiberglass insulated wall: 576 ft2 Surface area of Low-e windows: 144 ft2 Total Heat Gain by Room (wall + windows): = 32.694 kW into room EER = 10 COPR=2.93 W’net,in = Q’R / COPR = 32.694 kW / 2.93 = 11.155 kW (11.155 kW)(14 hours) = 156.17 kWh (156.17 kWh)($0.0955/kWh) = $14.914/day = ($14.914/day)(130 days/summer) = $1938.9 per summer season. The carrier system we have chosen has an EER of 12 more than the average cooling system. This leads to a savings of $8.134 / day, and a savings of $1057.70 / summer.

Lighting Maximizing day lighting, implementing energy efficient lights and installing proper controls are all different improvements that could be made to help create a more efficient room.

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Day lighting is the first option that should be looked at when efficiency is being looked at. Day lighting can help reduce the amount of actual lighting that is required and cause a decrease in energy and costs. Day lighting is dependent on the environment around the room and also the material being used for the windows. If properly implemented and designed, day lighting can eliminate a lot of unnecessary lights that are used within the rooms depending on the amount of light transmitted through the windows. Implementing energy-efficient lights is very important when discussing improving lighting options within a room. There are multiple variables that need to be looked at during There are various types of lighting sources available in the market today. See (Appendix 1)

http://www.aps.com/main/_files/services/BusWaysToSave/Lighting.pdf

Fluorescent Light bulbs are currently the best light bulbs for design purposes for a class Characteristics of Common Light Sources Light Source

Efficacy (Lumens/Watt)

Average Lamp Life (Hours)

Standard Incandescent 5-20 750-1000 Tungsten-Halogen 15-25 2000-4000 Compact Fluorescent 20-55 10,000 Tubular Fluorescent 60-100 15,000-24,000 Mercury Vapor 25-50 Up to 24,000 Metal Halide 45-100 10,000-20,000 High Pressure Sodium 45-110 Up to 24,000 room because of its high efficacy (lumens/watt) and huge increase in lifetime.

Color Rendering Index 100 100 80 50-90 15-30 60-90 9-70

Light Source Efficacy:

Efficacy= (Amount of Light Output)/ (Electricity Consumed) [LUMENS/WATT]

Due to their high efficacy, they produce much less heat than other light sources. The energy not used to produce light is converted to heat. This is an example of first law of Thermodynamics;

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“Energy can neither be created nor destroyed during a process; it can only change forms”. (Thermo Book Page 70)

Another factor that affects lighting is the ballasts that it operates on. A ballast help maintain the current flow in the bulbs. There are generally two types of ballasts that fluorescent bulbs are attached to in the market, which are, magnetic and electronic. Magnetic ballasts are less efficient than electronic ballasts. Magnetic Ballasts also have fewer options such as dimming and are also noisier. Electronic Ballasts are more expensive but does save energy and reduce energy costs.

http://nemesis.lonestar.org/reference/electricity/fluorescent/components.html

Please see Appendix 2 for Cost Effectiveness of Different Ballasts

Performance

Cost-Effectiveness Example Base Model Recommended Level T12,34 watts, magnetic T8,32 watts, electronic

Best Available T8,32 watts, electronic

Lamp and Ballast Type ballast

ballast

ballast

5300 lumens

5600 lumens

6000 lumens

4738 lumens

5018 lumens

5256 lumens

82 watts 295 kWh $17.70

62 watts 223 kWh $13.40

57 watts 205 kWh $12.30

Rated Lamp Output 2 Lamps Actual Light Output with Ballasta Input Power Annual Energy Usage Annual Energy Cost

http://www1.eere.energy.gov/femp/procurement/eep_fluortube_lamp.html

Implementing light controls is another option on how we increase efficiency of campus rooms.

Dimming controls and occupancy sensors are two simple solutions to saving energy. Dimming controls help to create an ideal lighting environment for anyone in the room. Instead of running at the maximum voltage, it will run at a lower voltage with more desirable lighting output. The lower the voltage input, the less energy it will need for running the lighting. More often than not, lighting can be lowered without affecting vision in the classroom.

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Occupancy sensors are really effective lighting controls as well. These sensors are very helpful on campus environments because of constant occupancy change within class rooms. Occupancy sensors limit energy usage by shutting off energy to the light bulbs when the room is unattended or unoccupied. These sensors use an IR (Infra red) sensor and work effectively because of high field of vision (150 degrees +) (APPENDIX 3)

Cost and Energy Analysis on switching Light bulbs

Assumptions

1. New Light -T8 32 W vs. Standard= T12 34 W 2. School Operation Hours= 2880 h/year 3. Estimated cost of electricity=$.09/kwh 4. Number of Lamps= 40 Wattage reduction = (Wattage reduction per lamp)(Number of lamps) = (34 - 32 W/lamp)(40 lamps) = 80 W Energy Savings = (Total wattage reduction)(Ballast factor)(Operating hours) = (.08 kW) (1.1)(2880 h/year)

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= 253.44 kWh/year Cost Savings = (Energy savings) (Unit electricity cost) = (253.44 kWh/year) ($0.09/kWh) = $22.80/year Implementation Cost = (Cost difference of lamps) (Number of lamps) = [($2.99-$1.99)/lamp] (40 lamps) = $40 Payback Period= (Implementation Cost)/ (Annual Cost Savings) = ($40/$22.80/year) = 1.75 Years

Cost and Energy Analysis on adding Occupancy Sensor Assumptions 1. 32 Watt Lamps with a 1.1 Ballast Factor 2. Hours used=1920 In Class Hours 3. Energy Cost= .09/kwh Energy Savings = (# of lamps)(Lamp wattage)(Ballast Factor)(Reduction of operating hours/yr) = (40 lamps)(32 W/lamp )(1.1.)(1920 hours/year) = 2703.36 kWh/year Cost Savings = (Energy Savings)(Unit cost of energy) = (2703.36 kWh/year)($0.09/kWh) = $243/year Average Implementation Cost = Material + Labor = $32 + $40 = $72 Payback Period= (Implementation Cost)/ (Annual Cost Savings) = ($72)/($243/yr) =.296=3.5 Months After doing a cost and energy analysis on adding a occupancy sensor( Appendix 7), the payback for the occupancy sensor will be in 3.5 months. After the payback, the room will save

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$243 per year. In a campus of multiple buildings with hundreds of rooms, these energy savings can amount to a vast amount. Multiple studies were done across the country which proved that students performance increase in more lighting friendly environments. With more day lighting and dimming options, students can be more comfortable. Fluorescent light bulbs can also be similar to daylight tones instead of the bright white tone they are familiarized with. According to experts at Carnegie Mellon University, “the average productivity impacts found by Carnegie Mellon in the 25 studies reviewed for lighting impact was 3.2% and, separately, temperature control impact on productivity is 3.6%. Another area of productivity impact evaluated by Carnegie Mellon found an average productivity gain from improved day lighting and control of 11% in 5 studies reviewed.102 Improvements in acoustics and reduced noise in schools also have been found to improve the quality of learning environments.”(Pg. 39-40 National Review of Green Schools: Costs, Benefits, and Implications for Massachusetts)

Impact Statement Improving lighting in campus rooms can have a huge effect on a college environment. The benefits include energy savings and a better learning environment. Switching light bulbs and instituting occupancy sensors is the bulk of energy savings for a room. After doing a cost and energy analysis on switching light bulbs (Appendix 6), it will save the university $22.80 per year after the initial payback of 1.75 years.

Improving the HVAC system has a tremendous positive impact. It benefits the University by saving it thousands of dollars a year. Moreover, it creates an ideal learning environment for students, allowing them to perform better on examinations, and stay alert in class. Studies have shown that the air quality and temperature in a school environment greatly affects student aptitude.

Conclusion

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Any temperature regulated room represents a thermally dynamic system with various energy inputs and outputs. The goal of this report is to analyze different building elements to construct a thermally efficient classroom, i.e. reduce the energy requirements of the room while also reducing energy loss. The three areas that mainly affect this are insulation, lighting, and HVAC systems. Proper insulation plays the biggest role in preventing energy waste; it prevents heaters from over working in the winter and air conditioners from over working in the summer. Foam insulation can approximately halve the energy lost from loose fill insulation, and is even more efficient than standard fiberglass. The downside to this is that the foam insulation is much more expensive. While the energy savings will defray the initial cost over the life time of the building, using foam may require too much of an initial investment, especially if used throughout a large structure. Efficient lighting sources can dramatically cut down on the power requirements of a classroom. The most efficient source would be to use daylighting, but this not always possible or practical. The best bet would be to use high efficiency fluorescent bulbs. These bulbs have very high lumen/watt ratios when compared to other sources, such as incandescent bulbs. LEDs can have efficiencies just as high as fluorescent bulbs, but remain expensive and require large arrays to light large areas. All of these elements can be considered part of a new wave of “green” engineering – building structures that do not waste energy and have little negative impact on the environment. For many, the ultimate goal of green engineering is to create a so-called zero energy building. Such a building would provide its own power and not draw anything off the power gird. While the field of green engineering is beyond the scope of this report, it is important to note that the elements discussed here play a critical role in the design of environmentally friendly structures.

Future Work There were several assumptions made during the analysis of this project. All the heat transfer equations assumed that the room was tightly sealed and disregarded any heat loss do to convection or radiation. These are obviously idealized conditions. Further research into the

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properties of airflow into and out of the classroom are needed to construct a more accurate thermodynamic model. This includes any air leaking through cracks in the walls or improperly sealed windows. Convective effects become very important if one tries to model the room with all the windows open. For the HVAC system, variables such as humidity, pressure gradients, and air density all must be taken into account. Also, the amount of direct sunlight incident on the room needs to be specified. In a real world situation, the side of the building the room is on would only receive direct sunlight for a portion of the day. The change of daylight with the change of seasons must also be considered for a more accurate model. This report compares the thermal efficiency (and thus the cost effectiveness) of new building materials versus preexisting ones. While the results show that long term energy savings eventually defer higher initial material costs, no cost analysis is considered for renovating existing structures. Such a cost analysis would have to be done on a case-by-case basis to account for labor costs and the specific geometry of each room. In order to make a room, and indeed an entire building more thermally efficient, there exist numerous novel devices to conserve heat. The products described in this report are elements used to reduce the energy requirements of a room. Devices such as hot water heat recyclers and seasonal thermal stores can be used to increase the thermal efficiency of a building as a whole. It was recently announced that new Drexel campus buildings will be designed to be “environmentally friendly”. The new integrated science building on 33rd and Chestnut St. will include features such as a biofilter wall – a wall of vegetation that naturally processes air. It would be interesting to find out what other features will be included in this building, and what types of energy efficient materials Drexel designers intend to use.

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1

www.usgb.org: “Why Build Green.”

2

http://www.rssweather.com/climate/Pennsylvania/Philadelphia/

3

http://hyperphysics.phy-astr.gsu.edu/hbase/hframe.html

4

“Thermodynamics: An Engineering Approach, Sixth Edition, pg 94

5

http://hyperphysics.phy-astr.gsu.edu/hbase/hframe.html

6

http://www.eere.energy.gov/consumer/your_home/insulation_airsealing/index.cfm/mytopic=11340

7

http://www.ornl.gov/sci/roofs+walls/insulation/ins_08.html

8

http://www.powerhousetv.com/stellent2/groups/public/documents/pub/phtv_se_in_bu_000574.hcsp

9

http://www.commercialwindows.umn.edu/issues_energy1.php

10

http://www.leeric.lsu.edu/energy/windows/

11

www.wikipedia.com, Vapor Compression Refrigeration Cycle

5

12

http://www.commercial.carrier.com/commercial/hvac/product_physical_data